I Want to Access Walk Mode in Texture Paint Mode With Shift + F
Using the Spacebar menu > Walk Naviation (you have to use type search, see more here) will do the trick. There is currently no shortcut for this in texture mode. 

If you want to add or override a shortcut for it, we can do this in the user preferences, File>User Preferences or Ctrl-Alt-U.

(Note: Opening up a new instance of blender is a good idea if you don't want to mess up you startup file)

Go into the input tab. Tab into 3D view and then into image paint. Next look for the shortcut you want to override, if it is not there, use add new.



Fill out the above form with the infromtaion, be sure to enter view3d.navigate into the little text box.